It is conventionally known to display created numerical control (NC) data on a screen of, e.g., an automatic programming apparatus for operator's visual inspection for validity/invalidity checking of the NC data. NC data is usually large in data quantity and cannot be displayed on the screen at one time. Conventionally, therefore, NC data corresponding to one screen capacity is first displayed and checked, and then next NC data corresponding to one screen capacity is displayed on the screen. Accordingly, the execution of the NC data is temporarily stopped while the NC data corresponding to one screen capacity is displayed, and the execution of the NC data for the next screen display is restarted only after the checking of the preceding data is completed. In case that NC data is displayed screen by screen as mentioned above, it is sometimes difficult for the operator to recognize the relation of the NC data that appears in different screens. To reduce this inconvenience, an attempt has been made to display the NC data block at the beginning of the next screen, in addition to the currently displayed NC data, as shown is FIG. 6.
As NC data consists of data items of different importance, the operator pays special attention to specific NC data items of great importance, when checking the validity/invalidity of the NC data. According to the aforesaid conventional method, however, since NC data corresponding to one screen capacity is displayed on the screen at one time, it is difficult to visually identify the specific data among a large number of data items.
An NC data execution method capable of reducing the above difficulty is also known, in which after the checking of one block of NC data displayed on the screen is completed, the next block of NC data is displayed (FIG. 7), whereby the operator's burden associated with visual checking is more or less reduced. According to this conventional method, however, the execution of NC data is interrupted each time one block of NC data is displayed. Thus, the operator must operate the automatic programming apparatus each time the checking of one NC data block is completed, to restart the execution of the NC data for display of the next data bock, thus making an efficient checking operation difficult.